PURPOSE: To provide a burring device which can form a cylindrical member whose ratio of the height to the diameter is more than 1 from a metal plate.
CONSTITUTION: In a burring device for producing a cylindrical member by forming a circular metal plate 10 having a through hole on the canter part, the device has a punch 12 of a cylinder shape which presses the center part of an end face of the circular metal plate and forms the internal circumferential face of the cylindrical member, and a die 20 which holds, at least, the neighborhood of the external circumference of the other end face of the circular metal plate and forms the external circumferential face of the cylindrical member by introducing the circular metal plate into the die hole 21 received by the pressing force of the punch. In the section of crossing the die 20 by the center line of the die hole 21, the radius of curvature on the side adjacent to the opening part of the circumference wall of the die hole 21 is small and the radius of curvature on the side far from the opening part is made larger than the radius of curvature of the side near to the opening part of the circumferential wall of the die hole 21.
YOKOI MICHIHARU
TAKIMOTO KOJI
